BIO112 Intro to the Oceans

How do oceans influence the planet

70% Earth's surface covered in water

Extensive biomass of photosynthetic organisms

Regulates climate/atmosphere (heat/carbon store)

What is the importance of the oceans to humanity

- fisheries

- aquaculture

- global trade

- energy potential

Examples of biological advances from the marine realm

- developmental biology = molluscs

- immune system = sea anemones

- fertilisation = sea urchin eggs

- neuroscience

Is there only one ocean?

it's all connected but not homogenous

What is the geological distinction between ocean and continents?

continental crust

- granite

- lower density

- thicker

- can be geologically old

- light colour

- felsic (Na, K, Ca, Al)

oceanic crust

- basalt

- higher density

- thinner

- geologically young

- dark colour

- mafic (Fe, Mg)

Crust

oceanic and continental

Lithosphere

crust and uppermost mantle

tectonic plates

Athenosphere

upper mantle below the lithosphere

weak, allows plates to move

Who proposed uniformitarianism?

Charles Lyell

What is uniformitarianism?

Belief that Earth's geology shaped by gradual processes operating at the same intensity for millions of years

What did Alfred Wagner propose?

theory of continental drift

Pangea!

Continental drift

a series of large tectonic plates moving - involves the entire surface of the earth

What was proposed about tectonic plate theory in 1965

Sea-floor spreading

How can the reversals of the Earth's magnetic field be observed in the sea floor?

magnetic polarity at the time of cooling can be observed in magma in the sea floor

Sea floor spreading

a geologic process in which tectonic plates—large slabs of

Earth's lithosphere—split apart from each other

Where does seafloor spreading occur

at divergent plate boundaries

divergent plate boundary

Boundary between tectonic plates in which the two plates move away from each other, and new crust is created between them

What causes seafloor spreading?

mantle convection

mantle convection

the slow, churning motion of Earth's mantle

convection currents carry heat from the lower mantle and core to the lithosphere

tectonic plates

sections of the lithosphere that move

subduction zone

where 2 plates meet and 1 is subducted under the other

When an oceanic plate meets a continental plate, which will be subducted?

the oceanic plate always

shear boundary

two plates slide past each other creating extreme friction

what do shear boundaries cause

earthquakes

immense friction prevents them moving smoothly so they lock up until stress builds up and they break free

continental margin

a boundary between continental crust and oceanic crust

continental shelf definition

the shallowest part of the continental margin

very gently sloping continental crust

ends at the shelf break

continental shelf features

varying width

~8 % of ocean area

biologically richest part of the ocean

continental slope

the steep slope between the outer edge of the continental shelf and the deep ocean floor

submarine canyon

begin at continental shelf and cut across continental slope to its base

channel sediments to the deep sea

continental rise

thick layer of sediment piled up on the sea floor

from submarine canyons and currents

deep-sea fans

a deposit of sediment from submarine canyons

active margin

a continental margin that coincides with a plate boundary

steep continental slope and a trench

passive margin

a continental margin that is not a plate boundary

gentle continental slope and a continental rise

Abyssal plain definition

deep ocean floor

Abyssal plain features

supports a variety of life

relatively flat

BUT has:

- submarine channels

- low abyssal hills

- plateaus

- rises

- seamounts

- volcanic islands

How many ocean basins are there?

4

What are the ocean basins?

Pacific, Atlantic, Indian, Arctic

What is the Southern ocean?

a continuous body of water that surrounds Antarctica